The odds against Carl beating his friend in a round of golf are $8: 5$. Find the probability that Carl will lose.

To find the probability that Carl will lose, we need to convert the odds against him into a probability.

The odds against Carl winning are given as $8:5$. This means that for every 8 favorable outcomes (Carl losing), there are 5 unfavorable outcomes (Carl winning).

To calculate the probability of Carl losing, we divide the number of unfavorable outcomes by the total number of possible outcomes. In this case, the total number of outcomes is the sum of the favorable and unfavorable outcomes, which is 8 + 5 = 13.

Therefore, the probability that Carl will lose is 8/13.